1. Field of the Invention
The present invention relates to a small-sized spindle motor employed for a disk player, more particularly to a spindle motor which has a more compact structure due to a decrease of its height.
2. Description of the Related Art
In general, an optical disk is capable of high-density recording and reproducing as compared to a magnetic recording tape and a LP and can be stored semi-permanently. Due to its merits, recently, disk players utilizing optical disks have been being widely spread.
Such a disk player includes a laser disk player, a compact disk player and a DVD (digital versatile disk) player and the like. Among such optical disk players, particularly, compact disk players, which have a small size and are portable, have been being widely spread. Recently, however, DVDs, which have the same size as compact disks while having a larger memory capacity than the compact disks, are being rapidly spread.
Disk players of this type are being minimized in size, height and weight so that users can carry them conveniently, and, in the future, slim type disk players having a 9.5 mm height are expected to form the mainstream.
One of the most important components in this disk player is a spindle motor for a drive for rotating a disk at a high speed without a movement. Spindle motors are also being miniaturized so as to conform to the miniaturization of disk players.
Of course, the miniaturized spindle motors have to be developed such that they can show a high-speed performance at a minimum current though its size becomes smaller, minimize vibration generated during driving and prevent the deviation of a disk during high speed driving.
FIG. 1 is a side cross-sectional view illustrating a conventional spindle motor for a disk drive.
As illustrated therein, the spindle motor includes a deck plate 1 which has a circuit substrate mounted on the upper surface and is fixed to a disk player (not shown) and a shaft 10 rotatably disposed perpendicularly to the deck plate 1.
On the lower end face of the shaft 10 is disposed a thrust bearing 11 for preventing the friction between the shaft 10 and the deck plate 1. To the lower end of the shaft is engaged a stopper ring 12 for preventing the shaft from deviating upwardly by a centrifugal force generated during high-speed rotation.
And, the spindle motor also includes a stator 20 composed of a cylindrical metal bearing 22 which is disposed on the outer peripheral surface of the shaft 10 and supports the shaft 10 so as to stand vertically, a cylindrical holder 24 disposed on the outer peripheral surface of the metal bearing 22 and a core 28 wound with coils 26 which is disposed on the outer peripheral surface of the holder 24 and generates a magnetic force by an applied power.
Additionally, a cap type rotor 40 of metallic material is coupled to the upper end of the shaft 10 so as to be located at the upper part of the stator 20. The rotor 40 and the shaft 10 are integrally formed because the shaft 10 is press-fit to the inner peripheral surface of a cylindrical boss 42 protruding at the center portion of the rotor 40.
Moreover, a magnet 45 is disposed on the inner peripheral surface of the rotor 40 so that it can be opposed to the core 28 of the stator 20 with an air gap therebetween. A pulling magnet 30 is disposed on the upper part of the stator 20 and pulls the rotor 40 downward by a magnetic force.
Meanwhile, on the upper surface of the rotor 40 is disposed a turntable 50 which is fixedly installed integrally with the rotor 40 and mounts a disk (D). The turntable 50 includes a disk chuck 52 on which the disk (D) is centered so as to be mounted at the precise position of the turntable 50, a jaw 54 which is slidably disposed at the disk chuck 52 and fixes the disk (D) mounted on the disk chuck 52 and a disk seat 56 which supports the mounted disk (D) from a lower side.
Of course, the jaw 54 is inserted into the lateral side of the disk chuck 52 along with a spring 54a and the disk seat 56 is formed in a flange extending from the lower part of the disk chuck 52 and is formed integrally with the disk chuck 52.
Here, the integral fixing of the turntable 50 and the rotor 40 will be explained in more detail. The disk chuck 52 is formed with a hub 52a penetrating through the center. After positioning the hub 52a of the disk chuck 52 at the boss 42 of the rotor 40, the boss 42 is press-fit to the inner peripheral surface of the hub 52a by pressurizing the disk chuck 52 from an upper side.
Of course, in order to press-fit the boss 42 of the rotor 40 to the hub 52a of the disk chuck 52, the outer diameter of the boss 42 and the inner diameter of the hub 52a must be made identical by precision finishing. Because the outer diameter of the boss 42 is the same as the inner diameter of the hub 52a, the disk chuck 52 is forced-fit to the rotor 40.
At this time, the disk chuck 52 is forced-fit to the rotor 40 after coating an adhesive (B) on the outer peripheral surface of the boss 42 of the rotor 40 so as to make the press-fit disk chuck 52 more firmly fixed thereto.
That is, the disk chuck 52 is firmly fixed by bonding-fixing the disk chuck 52 to the rotor 40 as well as press-fitting it thereto.
In the thus constructed conventional spindle motor for the disk drive, the disk (D) is fixed by centering a through hole formed at the center of the disk (D) on the disk chuck 52 of the turntable 50. During the fixing, the jaw 54 is slid into the lateral side of the disk chuck 52 via the through hole formed on the disk (D). Thereafter, when the centering is finished, the jaw 54 compresses the inside of the through hole of the disk (D) while slidably protruding to the outside of the disk chuck 52 by an elastic force of the spring 54a, thereby firmly fixing the disk (D).
Once the fixing of the disk (D) is finished, a power is applied to the coils 26 of the stator 20 to generate a magnetic force on the core 28. This makes the magnetic force of the core 28 and the magnetic force of the magnet 45 to interact with each other.
Then, the core 28 and the magnet 45 rotate the rotor 40 along with the shaft 10 at high speed by the interaction between their generated magnetic forces.
At this time, the shaft 10 can rotate at a high speed smoothly and vertically without movement by the metal bearing 22 disposed on the outer peripheral surface. Even if the shaft 10 is rotated at a high speed by the stopper ring 12 disposed at the lower end, it does not deviate upward.
That is, the metal bearing 22 supports the shaft 10 rotating at a high speed from the outer peripheral surface and the stopper ring 12 interrupts the shaft 10 from being lifted by a centrifugal force caused by the high-speed rotation.
The rotor 40 rotating at a high speed along with the shaft 10 is also likely to be lifted by the centrifugal force caused by the high-speed rotation, but is prevented from being lifted owing to an attractive force of the pulling magnet 30.
By the rotation of the rotor 40, the turntable 50 fixedly disposed on the upper surface of the rotor 40 rotates and the disk (D) mounted on the turntable 50 also rotates at a high speed along with the turntable 50. Therefore, the disk player (not shown) can records data on the disk (D) or reproduce the recorded data within a short time.
Of course, the disk (D) is firmly fixed by the jaw 54 of the turntable 50, so it is not lifted or deviated from the turn table 50 even when rotated at a high speed. Also, it is not lifted or deviates by a disk clamp (not shown) pressurizing the disk (D) from an upper side.
However, in the above-described conventional spindle motor for the disk drive, when the boss 42 of the rotor 40 is forced-fit to the hub 52a of the disk chuck 52, the adhesive (B) coated on the boss 42 is all squeezed out downward and is aggregated at one portion of the upper surface of the rotor 40.
Therefore, the turntable 50 is not tightly fixed to the upper surface of the rotor 40 by the adhesive (B) aggregated on the upper part of the rotor 40, but is fixed thereto, being lifted upward as much as the thickness of the adhesive (B) and accordingly there occurs a problem that the height (h) of the spindle motor is also increased as much as the lifted length of the turntable 50.
And, since the adhesive (B) is aggregated on one portion of the upper surface of the rotor 40, the adhesion surface area of the disk chuck 52 is decreased to thus cause the weakening of the adhesion force. This leads to a problem that the turntable 50 deviates from the rotor 40 by a centrifugal force during high-speed rotation of the rotor 40 to thus reduce the life span of the spindle motor.